linux-kernel - Re: [PATCH bpf-next v1 1/2] bpf: sock ops: add netns in bpf context

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Message-ID: <CAADnVQLzNotsJgniQc0cA0v8K=F0wwfOaT6KirRJ0urLiFib_Q@mail.gmail.com>
Date:   Tue, 16 Apr 2019 19:59:49 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Alban Crequy <alban.crequy@...il.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alban Crequy <alban@...volk.io>, iago@...volk.io
Subject: Re: [PATCH bpf-next v1 1/2] bpf: sock ops: add netns in bpf context

On Fri, Apr 12, 2019 at 3:01 AM Alban Crequy <alban.crequy@...il.com> wrote:
>
> From: Alban Crequy <alban@...volk.io>
>
> sockops programs can now access the network namespace inode via
> (struct bpf_sock_ops)->netns. This can be useful to apply different
> policies on different network namespaces.
>
> In the unlikely case where network namespaces are not compiled in
> (CONFIG_NET_NS=n), the verifier will not allow access to ->netns.
>
> Signed-off-by: Alban Crequy <alban@...volk.io>
> ---
>  include/uapi/linux/bpf.h |  1 +
>  net/core/filter.c        | 40 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 41 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 31a27dd337dc..5afaab25f205 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3069,6 +3069,7 @@ struct bpf_sock_ops {
>         __u32 sk_txhash;
>         __u64 bytes_received;
>         __u64 bytes_acked;
> +       __u64 netns;
>  };

stat /proc/self/ns/net
returns inode and device.
inum only is not enough to identify netns.
Both need to be exposed. See netns_dev/netns_ino in bpf.h